Power distribution or transmission lines are typically suspended from towers by insulators, which serve to electrically insulate line voltage from ground, and additionally prevent electrical power current from flowing from the distribution or transmission line to the supporting tower. Transient overvoltage conditions caused by current flows may lead to insulator flashover, resulting in a system outage and potential damage to the insulator and conductors.
To reduce or eliminate insulator flashover, a surge arrestor is typically used in parallel with an insulator. Surge arrestors are typically connected to power distribution or transmission lines to carry electrical surge currents to ground, and thus, prevent damage to the lines, as well as the equipment connected thereto. Surge arrestors generally offer high resistance to normal voltage across distribution or transmission lines, and provide very low resistance to surge currents produced by sudden high voltage conditions, such as those caused by a lightning strike, and thereby reduce the risk of insulator flashover during surge events. After the surge currents cease, the voltage drops and the surge arrestor returns to a high resistance condition. However, in certain cases when the surge arrestor fails, the high resistance condition is not resumed, and the surge arrestor continues to provide an electrical path from the distribution or transmission line to the ground. As a result of arrestor failure, the distribution or transmission line will lockout.
Disconnectors (or disconnecting devices) are commonly used in combination with the surge arrestors to separate failed surge arrestors from the circuit. The surge arrester/disconnector assembly is connected in parallel with the insulator. In certain arrangements, the surge arrestor is connected to the distribution or transmission line by a copper or aluminum line lead, a disconnector, and a number of moving, wearable connections between the components which include shunt bypass assemblies that provide solid, partial discharge free electrical contact around the associated moveable, wearable connections. The disconnectors provide a visual indication of surge arrestor failure upon actuation of the disconnectors. The disconnectors have an explosive charge to physically separate the terminals of the disconnector when actuated. Operation of the disconnector effectively removes the failed arrester from the circuit. Once the fault has been cleared, the power system circuit can be reenergized without the failed arrester in the circuit. In some cases, upon actuation of the disconnector, the line lead, which is still connected to ground, swings uncontrollably unless weights, such as chains, are attached so that the line lead falls to a safe location to prevent unintentional short circuits from accidentally coming in contact with a conductor. However, the weights on the line lead provide added mechanical stresses on the disconnector, as well as added costs due to added components.
Therefore, a need exist in the art for an improved line protection system that provides more reliable electro-mechanical connections between system components, reduces mechanical stresses on the disconnector, assures more effective disconnection of a failed arrestor, and is lower in cost than existing systems.